RFID systems are gaining in popularity for use in retail, commercial and health care service industries for applications such as point-of-sale data management, rental item tracking, baggage handling, real-time location systems and inventory management, or more broadly, supply chain management. An RFID system generally consists of transponders or tags containing a chip, wherein the chip holds data that can be read by an RF transceiver or reader when the transponder passes within range of the reader. The reader is provided with an antenna and processing logic for reading the data from the tag.
In typical embodiments, an RFID antenna emits radio signals to activate an RFID tag and read and write data to and from the tag. Antennas act as data conduits, part of a coupling for data communications, between tags and RFID readers. Antennas are available in a variety of shapes and sizes. Antennas in some embodiments are built into doorways to receive tag data from objects passing through doors or mounted on interstate tollbooths to monitor traffic passing by on a freeway. In some embodiments, where multiple tags are expected continually, the electromagnetic field produced by an antenna is constantly present. If constant interrogation is not required, the field can be activated by sensors.
An antenna is typically packaged with an RFID reader, which is, configured in various embodiments as a handheld or as a fixed-mount device. An RFID reader in typical embodiments emits radio waves in ranges of anywhere from one inch to 100 feet or more, depending upon its power output and the radio frequency used. When an RFID tag passes through the electromagnetic field of a radio signal from an RFID antenna, the RFID tag detects the reader's activation signal. The reader decodes the data encoded in the tag's integrated circuit and the data is passed to an appropriate component such as a system server for processing.
RFID transponders or tags come in a wide variety of shapes and sizes, and can be incorporated as part of contactless smart cards, smart labels, plastic or glass housings, key fobs, watches and the like. Readers can be hand-held, mobile devices or can be maintained in a fixed position.
RFID tags are categorized as either active or passive. Active RFID tags are powered by an internal battery and are typically read/write, i.e., tag data can be rewritten and/or modified. An active tag's memory size varies according to application requirements; some systems operate with up to 1 MB of memory. In a typical read/write RFID work-in-process system, a tag might give a machine a set of instructions, and the machine would then report its performance to the tag. This encoded data would then become part of the tagged part's history. The battery-supplied power of an active tag generally gives it a longer read range. The trade off is greater size, greater cost, and a limited operational life (which may yield a maximum of 10 years, depending upon operating temperatures and battery type, for example).
Passive RFID tags operate without a separate external power source and obtain operating power generated from the RFID reader. Passive tags are consequently much lighter than active tags, less expensive, and offer a very long operational lifetime. The trade off is that passive RFID tags have shorter read ranges than active tags and require a higher-powered reader. Some passive tags are programmed with a unique set of data (usually 32 to 128 bits) that cannot be modified. Read-only tags most often operate as a license plate or index into a database, for example, in the same way as linear barcodes reference a database containing modifiable product-specific information.